Four examples of prior art location-based information acquisition methods are now described.
Prior art 1 (JP-A 160076/1999) discloses a navigation unit that communicates with a destination facility (e.g. a restaurant) to send a predetermined message about a user name, reservation request and so on by e-mail when a vehicle on which the unit is mounted reaches within a predetermined distance from the destination facility on a map installed on the unit or the time required to reach the destination facility comes to a predetermined value.
However, in the navigation unit shown in the prior art example 1 there is a problem that its application is restricted or impractical since its terminal cannot know information about the facility that may be updated daily on the move automatically, moreover an address of the destination facility must be set in the navigation unit in advance, and therefore the navigation unit cannot cope with such changes as closing or establishment of facilities or alternation of the contents of the service provided.
Prior art 2 (ITS Congress '99 “Proposal of an Algorithm for Transmission and Cache of Location Dependent Data for In-Vehicle Computer System”) discloses another navigation unit that receives a series of information that is necessary for driving such as landmarks located in the traveling direction, maps and so on successively when the vehicle reaches predetermined positions. This unit receives the series of information that is transmitted from a database through networks by way of radiowave transmission facilities and so on placed along roads everywhere. Furthermore, as an extension of this method, this unit obtains data on positions along a planned route in advance and in a unit. This configuration may solve the problem that if the data concerning the planned route has not been obtained in advance, too much time may be taken to retrieve data concerning landmarks, maps and so on in a database after the vehicle has arrived a predetermined position, and to receive and display the data. Therefore, the data may be displayed only after the vehicle has passed the position corresponding to the data.
However, the method as shown in prior art 2 may have the following problems when the vehicle changes its route or stops driving:
(1) Communication may often be performed uselessly (communication costs may often be wasted);
(2) An extra memory is needed in every navigation unit to store data for, e.g., four nodes (crossovers) in advance;
(3) This method cannot be adapted when the driving route has not been fixed beforehand;
(4) Since it is not indicated who prepares and updates a database, this method may lack in operational feasibility;
(5) Since the contents of the database are permanent, the navigation unit according to this method is totally equal in terms of functions to the conventional navigation units that store the map database on a storage device such as a CD-ROM or a DVD permanently.
Next, prior art 3 (JP-A 307035/1998) discloses a system for determining a position of a vehicle equipped with a (GPS) Global Positioning System receiver at a center and informing the vehicle of appearance of an information providing spot in the neighborhood of the vehicle by any communicating means. For example, in this system, the center monitors when a landmark, such as a gas station, approaches and informs the vehicle of that situation by telephone, FAX or a pager and the like.
However, the system shown in prior art 3 has a problem that significant communication costs are wasted uselessly since the vehicle must transmit location information to the center continuously regardless of presence of the landmark in the neighborhood. Further, since conventional navigation units have already implemented a function to notify to the vehicle of the approach of the landmark (the gas station in this example) by setting the gas station as a passing point, there is no need to take a trouble to communicate with the center. Moreover, in this system shown in prior art 3, the mobile communication terminal cannot know information that is provided by facilities and that would be updated daily such as, for example, “today's gasoline price—90 yen/liter, Aug. 10, 2000”.
In addition, there has been another prior art wherein a mobile communication terminal unit that comprises a (PDA) personal digital assistant or a notebook PC equipped with communicating means such as a cellular phone or a PHS and so on, and position detecting means such as a GPS receiver and so on retrieves a facility such as a restaurant in the vicinity of the retrieving point on the Internet and displays the facility on a map in an overlapping manner. This system is intended to simply check whether there is a desired facility in the vicinity of a given position. The system may further be configured to display a detailed description when the user selects a mark of a particular facility.
However, the system described above has a problem that time-consuming manual operations and retrieval are needed to acquire information since the mobile communication terminal unit must access and retrieve sites on the Internet sequentially by manual operation while the mobile communication terminal unit moves. Further, it is not feasible because it may not be safe to operate the mobile communication terminal unit continuously while driving. Still further, timing to acquire the information may often be delayed in such system.
Each of the prior art location-based information acquisition methods as described above simply provides so-called landmark displaying function that gives notice when a predetermined destination facility approaches, or simply checks whether there is a desired type of facilities such as shops and restaurants in the neighborhood. Therefore, the information that is provided by the facilities and that would be updated daily or momentarily such as “today's articles for special sale till 5:00 p.m. are . . . ” cannot be recognized automatically and quickly just prior to passing in front of the facilities. Further, in such prior art methods, it is impossible to acquire peripheral information about the area where the vehicle enters successively and automatically.
In view of the foregoing, this invention has been made, and it is an object of this invention to solve the problems described above and provide a location-based information intermediation and acquisition method that can access a desired information source by synchronizing with behavior such as a present position or a moving bearing angle, and acquire location-based information (contents) automatically and quickly. Further, this invention provides a mobile communication terminal and an intermediation computer system for implementing such method.